I believe that telling the truth is the most important principle. Not only does my credibility as an engineer depend on the truth, the lives of the consumers of my products do as well. Society depends on us to make their lives easier by building various machineries and we depend on them for their financial support. It is a form of trust created throughout generations.  Companies may force employees to lie about their products to increase sales because they only care about the money. It is the workers who make the products have to live with the guilt of making products that are faulty. So the employees must tell the truth no matter the amount of pressure from the top officials. This applies to every single profession which involve consumers such as the medical field, food industry, etc. A scenario where telling the truth would be the most important ethical principle would be the production of  planes.